Dispersion comprising pigment,organic liquid and polymeric deflocculating agent

ABSTRACT

A DISPERSION COMPRISING A PIGMENT, AN ORGANIC LIQUID AND A POLYMERIC DEFLUOCCULATING AGENT COMPRISING A BACKBONE CHAIN HAVING INCORPORATED IN, OR DEPENDENT FROM IT, FIRSTLY A GROUP OF INTERNAL SALT STRUCTURE AND SECONDLY A SOLUBILIZING GROUP.

United States Patent Office 3,832,209 Patented Aug. 27, 1974 U.S. Cl.106308 Q 11 Claims ABSTRACT OF THE DISCLOSURE A dispersion comprising apigment, an organic liquid and a polymeric defiocculating agentcomprising a backbone chain having incorporated in, or dependent fromit, firstly a group of internal salt structure and secondly asolubilizing group.

This is a continuation of application Ser. No. 143,246 filed May 13,1971 and now abandoned.

This invention relates to dispersions of pigments in organic liquids.

Dispersions of pigments in liquid organic media comprising solutions ordispersions of film-forming polymer are used as paints, lacquers andprinting inks. In these compositions it is desirable that the pigmentparticles are defiocculated, that is, the particles be present asdiscrete, individual particles in the liquid organic medium, and shouldnot aggregate.

When pigments are dispersed in organic liquid media, suspensions arefrequently formed exhibiting some degree of aggregation of the pigmentparticles. Certain materials, for example, soya lecithin and metal soapsof fatty acids, have been proposed as additives to limited pigmentflocculation. However, in many systems, such as solutions of additioncopolymers in organic liquids, satisfactory deflocculated dispersions ofpigment cannot be readily prepared. Thus, for example, titanium dioxidepigment forms a highly flocculated dispersion in a solution comprisingpoly (methyl methacrylate) We have now found that certain polymerscomprising internal salts are unexpectedly effective as pigmentdeflocculating agents.

Accordingly we provide a dispersion comprising a pigment, an organicliquid and a polymeric defiocculating agent comprising a backbone chainhaving incorporated in, or dependent from, it, firstly a group ofinternal salt structure and secondly a solubilising group as hereinafterdefined.

The nature of the organic liquid used in preparing the dispersions ofour invention is not narrowly critical. The organic liquids normallyused in the preparation of conventional dispersions of pigments may beused. Thus suitable organic liquids include saturated hydrocarbons suchas aliphatic or alicyclic hydrocarbons; aliphatic oxygen containingorganic liquids, for example, alcohols, ketones, esters and ethers; andaromatic hydrocarbons; or mixtures thereof.

The function of the backbone chain is essentially that of a supportingstructure for the solubilising group and the group of internal saltstructure. Consequently the nature of the arrangement of the atomsforming the chain is not narrowly critical. Thus the chain may consistof carbon atoms alone, carbon atoms linked with one or more heteroatoms, in particular oxygen, nitrogen, sulphur, phosphorus, silicon andboron; alternatively it may consist of a series of alternating pairs ofP-O groups, Si-O groups or B-O groups. The backbone may be linear,slightly or highly branched, or cross-linked, provided how ever, thatthe resultant defiocculating agent remains soluble in the organicliquid. Convenient backbones may be inorganic and, preferably, organicpolymer chains; a wide range of polymers is useful as backbones, theprincipal limitation being that they must be capable of including asufficient number both of the solubilising groups as hereinafter definedand of the groups of internal salt structure.

The backbone may be formed from addition polymers, e.g. polyalkylenes,which may if desired bear substituents other than those above definedprovided these further substituents do not interfere with the solvationand salt forming properties of the solubilising groups and of the groupsof internal salt structure. The type of such further substituentsdepends on the monomer unit used to build up the backbone. Suitablebackbones are the carbon to carbon chains in polystyrene, polyvinylchloride, polyvinyl alcohol, poly-alpha-beta-ethylenically unsaturatedcarboxylic acid derivatives particularly substituted and unsubstitutedpolyacrylates, e.g. polymethyl methacrylate or polyacrylic acid; anothergroup of suitable polymeric backbones are the condensation products ofdicarboxylic acids with diols, dicarboxylic acids with diamines,polyurethanes comprising the reaction products of diisocyanates withreactive hydroxyl group containing diols, polyethers, polyesters orpolyamides; epoxy resins, polyethers, polyamines, polyureas,polysulphides, polyimides, polysulphones, polyoxyalkylenes, polyacetalsand alkyd resins. As above stated, it is, however, understood that thedefiocculating agents derived from said backbones must remain soluble inthe organic liquid and that the backbone must be capable of including aplurality of each of the solubilising group and the group of internalsalt structure. The backbones derived from addition polymers may be madeby homopolymerisation or copolymerisation.

The solubilising group is characterised by its ability to be solvated bythe organic liquid used in the manufacture of the pigment dispersion. Agroup is usually capable of being solvated if its composition isidentical with or chemically closely related to the composition of theorganic liquid. A test for selecting suitable solubilising groups isthat the compound, resulting from conversion of the solubilising groupinto a separate molecule bearing on the atom bridging it to the backbonea hydrogen atom or a low molecular Weight radical, e.g. methyl oracetyl, must be readily soluble in the organic liquid. By readilysoluble we mean having a solubility in excess of 20% by weight,preferably in excess of 50% by weight, most preferably completelymiscible in the organic liquid.

For example, when the organic liquid is a saturated hydrocarbon,suitable solubilising groups attached to the backbone directly orthrough linking groups are substituted or unsubstituted long chain alkylgroups. By long chain" we mean chains of more than six carbon atoms,e.g. 2-ethylhexyl, dodecyl, hexadecyl, stearyl or poly(l2- hydroxystearic acid) condensates.

Alkyl groups are also suitable solubilising groups for aliphaticoxygen-containing organic liquids but in this case the alkyl chainsshould contain more than four carbon atoms.

Additional suitable solubilising groups for use with aliphaticoxygen-containing organic liquids, such as alcohols and ketones, are forexample groups containing polyalkoxides prepared from monomers such asethylene oxide, propylene oxides or butylene oxides, or are for examplegroups containing alcohols, ketones or derivatives of ketones formed bythe reaction of formaldehyde with ketones. These oxygen-containingsolubilising groups may also be used with aromatic organic liquids.Additional suitable solubilising groups for use with aromatic organicliquids are phenyl and benzyl groups derived from aromaticallysubstituted ethylenically unsaturated monomers such as styrene and vinyltoluene.

The above examples illustrate suitable solubilising groups but do notlimit the scope of the invention.

The internal salt structure may be incorporated in the backbone chain.In this case the backbone chain contains one or more of the followinggroups:

wherein X is a cation, Z is an anion and Y is any suitable linkinggroup, Suitable groups X are, for example ammonium, sulphonium andphosphonium groups, preferably.

wherein W, R R R are as defined herein below. Suitable groups Z are acidresidues, preferably.

wherein W is any suitable linking group; R R R separately, is hydrogen,alkyl, aryl, aralkyl, alkenyl or acyl, two of which may be joinedtogether to form a ring; R is -OR R or '-O-; R being either alkyl oraryl, and wherein there may be two cations X to each dianion Z, wheneverR is O". The exact nature of X, Y and Z is not narrowly critical.

Alternatively the internal salt structure may be dependent from thebackbone chain. In this case the backbone chain contains one or more ofthe following groups:

wherein A and D are cations, B and E are anions and W, L and K are anysuitable linking groups as defined hereinbelow.

A may be for example, ammonium, sulphonium or phosphonium groups,preferably:

B may be for example, an acid residue, preferably,

%0 -COO-, --PO- or S 0:,

except that when A is B can not be SO 4 B may be for example an acidresidue, preferably 0- 0- -I] or -S.

D may be, for example, ammonium, sulphonium or phosphonium groups,preferably R1 R1 NqRz, '-S 0! P R1Z R3 R2 Ra R R and R are as definedhereinbefore. Suitable linking groups Y, W and L, are non-polar andcapable of forming two covalent bonds for example O-, S, CH CH or -CHSuitable linking group K is non-polar and capable of forming threecovalent bonds, for example,

The exact nature of the linking groups is not narrowly critical.

We have also found polymeric deflocculating agents of use in ourinvention wherein the group of internal salt structure is a groupcontaining both an acidic residue and a radical selected from the groupconsisting of amino, phosphino or mercapto.

The degree of ionisation of the polymeric defiocculating agents used inour invention is not critical and the agents remain effective underconditions of pH wherein the acidic residue and/or the amino, phosphinoor mercapto groups if present is undissociated.

Accordingly we provide a dispersion comprising a pigment, an organicliquid and a polymeric deflocculating agent comprising a backbone chainhaving incorporated in, or dependent from it, firstly a solubilisinggroup and secondly a group selected from the group consisting of --XYZ,-WA--L-B, WE-LD and wherein X, A and D, separately, is ammonium,phosphonium, sulphonium, amino, phosphino or mercapto groups; Z, B and Eseparately is an acid or acid salt but when A is ammonium, B cannot beSOY, W, L and K are linking groups.

Preferably the polymeric deflocculating agent comprises the group X-YZwherein X is selected from the group consisting of and wherein Z inselected from the group consisting of and wherein Y and W, separately,is a non-polar linking group capable of forming two covalent bonds; R RR separately, is hydrogen, alkyl, aryl, aralkyl, alkaryl or aryl, two ofwhich may be joined together to form a ring; R is OR 6 or R R beingeither alkyl or aryl.

In practice it is convenient to make the backbone of the deflocculatingagents by polymerising or, in the case of addition copolymers, bycopolymerising, the mer-units of the polymer which bear sites capable ofreacting with one or both of the desired types of substituents;alternatively met-units of the polymer may already bear a suitablesubstituent of a solubilising group and/ or a group of internal saltstructure prior to polymerisation.

The deflocculating agents may be prepared by methods well established inthe art by copolymerisation of comers containing solubilising groups andcomers which either contain internal salts or contain a structure fromwhich the internal salt may be formed. Two or more different comers maybe required for the formation of an internal salt in the final polymer.

Conventional addition polymerisation initiators, chain transfer agentsand techniques, including for example, skew feeding of monomers may beused. It is convenient to carry out the polymerisation in the presenceof a solvent for the polymer.

When the polymer is prepared by the copolymerisation of a mixture ofcomers comprising a comer containing the solubilising group or to whichthe solubilising group may be later attached and comers containing agroup of internal salt structure or to which a group of internal saltstructure may be later attached, comers containing a solubilising groupor to which a solubilising group may be attached should predominate inthe mixture of comers. The molar percentage in the mixture of the comerscontaining the solubilising group or to which the solubilising group maybe later attached should preferably be between 99 and 50. A mixture ofdifferent solubilising groups may be used.

The total molar percentage in the mixture of the comer or comerscontaining the internal salt group or to which the internal salt groupmay be later attached, should preferably be between 1 and 50.

The molecular weight of our polymeric deflocculating agents lies between2,000 and 500,000, preferably between 5,000 and 100,000. The comercontaining the solubilising group is such as to be soluble in theparticular solvent in which the pigment is to be dispersed. Forhydrocarbon solvents suitable comers are, for example, the long chainalkyl esters of acrylic, methacrylic, crotonic and other reactiveolefinic acids, and the vinyl esters of long chain carboxylic acids. Bylong chain we mean chains of more than six carbon atoms, e.g.Z-ethylhexyl, dodecyl, hexadecyl or stearyl.

Thus, examples of suitable comers containing a solubilising group forsaturated hydrocarbons are lauryl acrylate, 2-ethylhexyl acrylate,2-ethylhexyl methacrylate, vinylstearate, tetradecylcrotonate, octadecylmethacrylate and glycidyl methacrylate condensates of l2-hydroxy stearicacid.

The nature of the pigment to be used in the dispersion is not criticaland the following are examples of suitable materials:

(i) inorganic pigments, e.g. titanium dioxide, oxides and hydratedoxides of iron, lead chromates, zinc chromate and Prussian Blue;

(ii) extender pigments, e.g. barytes, silica, whiting, blanc fixe,alumina and the aluminium silicates; and

(iii) organic pigments, e.g. azo, vat, quinacridone and phthalocyaninepigments.

The dispersion may be prepared by grinding together, preferably underhigh-speed mechanical stirring, the pigment, organic liquid anddeflocculating agent.

Accordingly we provide a process of manufacture of a pigment dispersion,which process comprises grinding a mixture comprising an effectiveamount of polymeric defiocculating agent, pigment and organic liquid.The maximum concentration of deflocculating agent to be used is notcritical, although it is not economic to use an excess over thatrequired for a particular application. The minimum concentration is, atleast in part, related to the specific surface area of the pigment. Theactual-optirnal or most economicalamount of deflocculating agent to beused with a particular pigment/organic liquid system is readilydetermined by simple experiment. Incremental additions of deflocculaingagent are made to the system until the desired level of defiocculationis attained. The invention is not limited to the preparation of fullydeflocculated dispersions as for many purposes it is not necessary noreconomically desirable to prepare a fully deflocculated system.

In practice, we have found that the amount of deflocculating agentrequired to give satisfactory dispersions is between 0.001 and 0.05grams of solid deflocculating agent for every 10 square metres ofpigment surface area.

Alternatively we provide a process of manufacture of a pigmentdispersion, which process comprises grinding a mixture comprising apigment, an effective amount of deflocculating agent, inorganic base andorganic liquid. The inorganic base may be an alkaline earth, or alkali,metal hydroxide, for example, calcium hydroxide or sodium hydroxide. Webelieve that the deflocculating agent in these dispersions comprises aninternal salt structure wherein the basic group is not quaternised andthe acid group is the salt of the alkaline earth, or alkali metal. Theamount of base added is not critical but we prefer to use substantiallyequimolar amounts of base and polymeric deflocculating agent.

We have found that the pigment dispersions prepared from pigmentparticles coated with the polymeric de fiocculating agent have improvedproperties.

Accordingly We provide a process of preparing a pigment dispersion whichprocess comprises firstly, coating the pigment with a polymericdeflocculating agent as hereinbefore described and secondly, grindingtogether a mixture comprising the coated pigment, an organic liquid,optionally inorganic base and optionally water.

The dispersions of this invention are of use, for example, asconcentrated tinting bases for paints and printing inks. For thisapplication we prefer to use deflocculating agents in which theconcentration of internal salt groups approaches the upper limit of ourpreferred range. It is a particular advantage of our invention thatthese deflocculating agents are usually accepted by a wide range offilm-forming vehicles, thus providing unusually versatile tinting bases;in particular they provide a convenient route to the preparation ofdeflocculatcd pigment dispersions in solutions of addition polymers inorganic liquids. The concentration of pigment in certain cases may be asmuch as 4060% by volume; consequentlly our invention affords an increasein production capacity of dispersing equipment, and the dispersionsrequire less space for storage.

In a further embodiment of our invention, using a filmformingdeflocculating agent, the deflocculating agent may provide the Whole orpart of the film-forming polymer of a paint. That is, a dispersion ofpigment in an organic liquid and deflocculating agent, optionally in thepresence of a minor proportion of additional film-forming polymer, whenapplied as a film to a substrate and allowed to dry in air, forms on thesubstrate a coherent decorative and/or protective coating. In thisapplication we have found it preferable to use low concentrations, i.e.approaching the minimum concentration limit of internal salt groups inthe deflocculating agent, which is itself used in the dispersion inrelatively high proportions, for example, the pigment volumeconcentration based on the total solids content of the dispersion may befrom 8 to 25%, and the deflocculating agent volume concentration basedon the total solids content of the dispersion may be as high as 92%.

The activity of the deflocculating agents is in some cases improved bythe presence of a small amount of water in the dispersion. Under suchcircumstances we prefer the amount of water in the dispersion to be inthe range from 0.05 to w./w. inclusive more preferably in the range from0.5 to 2% w./w. inclusive. In dispersions prepared from commerciallyavailable materials there is normally sufiicient water present but, ifdried materials are used, additional water may be added with advantage.In certain cases the activity of the deflocculating agents improves onkeeping the dispersion for a period of time before use.

Our invention is now illustrated, but in no way limited, by thefollowing examples, in which all parts and percentages are given byweight unless otherwise specified.

EXAMPLE 1 Dimethylaminoethyl methacrylate (47.1 parts) was placed in astirred reaction vessel fitted with a stirrer and reflux condenser andmixed with benzyl chloride (37.8 parts), benzene (150 parts) and TopanolA (trademark of Imperial Chemical Industries Limited for 2,6-ditert.butyl-4-methylphenol) (0.1 part). This mixture was heated under refluxwith stirring for one hour, the quaternary ammonium salt so formedseparated out from the solution as a white solid and after cooling wasremoved by filtration.

EXAMPLE 2 A mixture of comers consisting of the quaternary salt (80parts), as prepared in Example 1, methacrylic acid (25.8 parts) and2-ethylhexyl acrylate (331 parts) was added to a stirred reaction vesselfitted with a reflux condenser and containing toluene (400 parts) andn-propanol (400 parts). Azodiisobutyronitrile (4 parts) was added andthe mixture heated under reflux with stirring. Three further portions (4parts) of azodiisobutyronitrile were added at three hourly intervals.After an additional three hours the polymerisation was substantiallycomplete. A large excess of aqueous calcium hydroxide solution was addedwith stirring and the water was removed by azeotropic distillation toyield a 20% solution of the polymer in toluene.

The solution was filtered to remove inorganic solids to give a slightlygelatinous solution. This contained some calcium ions and was used asdeflocculating agent A.

EXAMPLE 3 Dimethyl sulphate (43.2 parts) was added slowly to a mixtureof Z-methylthioethyl acrylate (50 parts) and benzene (50 parts) in astirred reaction vessel fitted with a reflux condenser. The mixture wasstirred at room temperature for one hour and the resultant sulphoniumsalt separated out as a white solid and was removed by filtration.

EXAMPLE 4 Example 2 was repeated except that in place of the mixture ofcomers used in that Example the mixture of comers used was a mixture ofthe sulphonium salt prepared in Example 3 (48.3 parts), Z-ethylhexylacrylate (331 parts) and methacrylic acid (25.8 parts). The resultantsolution contained 20% polymer in toluene and was used as deflocculatingagent B.

EXAMPLE 5 Example 2 was repeated except that in place of the mixture ofcomers used in that example the mixture of comers used was prepared bythe separate, simultaneous addition, into the stirred reaction vesselcontaining toluene (400 parts) and n-propanol (400 parts), of a solutionof allyltriphenylphosphonium bromide (22.7 parts) in n-propanol 100parts) and of a mixture of methacrylic acid (6.5 parts) and2-ethylhexylacrylate (83 parts).

The resultant solution contained 20%; polymer and was used asdeflocculating agent C.

8 EXAMPLE 6 Example 2 was repeated except that in place of the mixtureof comers used in that example, the mixture of comers used was preparedfrom Z-ethylhexyl acrylate (83 parts), glycidyl methacrylate (16.2parts) and the quaternary salt (21.2 parts) of dimethylaminoethylmethacrylate and benzyl chloride.

The resultant solution contained 35% polymer in toluene.

EXAMPLE 7 A portion (72 parts) of the polymer solution prepared inExample 6 was added dropwise with rapid stirring to a reaction vesselcontaining 98% sulphuric acid (5.6 parts). After 15 minutes the mixturewas washed with water three times and with aqueous sodium hydroxidesolution once. The solution of organic material was dried by azeotropicdistillation with toluene. The resultant solution contained 10% w./w.polymer in toluene and was used as deflocculating agent D.

EXAMPLE 8 Example 7 was repeated except that instead of the sulphuricacid used in that example, w./w. phosphoric acid (6.5 parts) was used.

The resultant solution contained 10% w./w. polymer in toluene and wasused as deflocculating agent E.

EXAMPLE 9 Example 5 was repeated except that instead of the methacrylicacid used in that example, glycidyl methacrylate (10.7 parts) was used.

A portion of the resultant solution (72 parts), containing 35 polymer intoluene, was reacted with 85 w./w. phosphoric acid (6.5 parts) asdescribed in Example 8.

The resultant solution contained 20% w./w. polymer in toluene and wasused as deflocculating agent F.

EXAMPLE 10 Dimethylaminoethyl methacrylate (82 parts) was placed in astirred reaction vessel fitted with a stirrer and reflux condenser andmixed with chloracetic acid (49 parts), n-propanol (131 parts) andTopanol A (0.3 parts). This mixture was heated under reflux and stirredfor one hour.

A mixture of 2-ethylhexyl acrylate (322 parts), azodiisobutyronitrile(0.4 parts), acetone (3 parts), and all the solution prepared above, wasadded to a stirred reaction vessel fitted with a reflux condenser,containing toluene (300 parts) and n-propanol (400 parts). The mixturewas heated under reflux.

Three further portions (0.6 parts) of azodiisobutyronitrile were addedat three hourly intervals. After an additional 2 hours thepolymerization was substantially complete. A slurry of sodiumbicarbonate (55 parts) in water (200 parts) was added and the waterremoved by azeotropic distillation with toluene. The resultant solutioncontained 30% w./w. polymer in a mixture of toluene and propanol and wasused as deflocculating agent G.

EXAMPLE 11 The deflocculating agents A, B, C, D, E, F and G prepared inExamples 2, 4, 5, 7, 8, 9 and 10 respectively were tested as dispersantsfor Austiox R-CR (trademark of Australian Titan Products Ltd. for rutiletitanium dioxide) in xylene. The following general procedure wasadopted. A mixture of Austiox R-CR 80 g.) and deflocculating agent (8g.) was made up to 100 parts with xylene. This mixture was shakenvigorously using a Red Devil (Trademark) paint conditioning machine in a750 ml. bottle containing 200 g. of 8 mm. glass balls for 30 minutes.The pigment dispersion obtained was assessed for fineness of grind andviscosity. A grading of 10 means that the dispersion was very fine andof low viscosity. A grading of 1 means that the grinding was coarse andthe viscosity high. A grading of 0 means the powder was undispersed. Anydispersant giving a grading of more than has excellent dispersantproperties. The control dispersion was one made up without using anydispersant. The results are given in Table 1.

in place of the sodium hydroxide. The resulting solution was used asdefiocculating agent].

EXAMPLE 16 A mixture of 4-vinyl pyridine (19.7 parts), 2-ethylhexylTABLE 1 5 acrylate (207 parts), styrene (78 parts), methacrylic acidDefiocculatmg agent: Gradmg (16.2 parts), azodiisobutyronitrile (3.3parts), acetone control g (20 parts) and n-propanol (50.0 parts) wasadded over A 7 3 hours to a stirred refluxing mixture of n-propanol (340B 7 10 parts) and toluene (340 parts) contained in a reaction C vessel.Portions of azodiisobutyronitrile (0.6 part) were D 6 added to therefluxing mixture every half hour for 5 E 6 hours, when polymerisationwas substantially complete. F 5 The n-propauol was then removed byazeotropic distilla- G 8 tion with toluene to yield a solutioncontaining 30% W./w. EXAMPLE 12 polymer in toluene which was used asdefiocculating The defiocculating agents A, B, C, D, E, F and G P agentK. EXAMPLE 17 pared in Examples 2, 4, 5, 7, 8, 9 and 10 respectively,were tested as dispersants for carbon black in xylene. A portion 100parts) f h polymer solution The Same lil'oce/dllle was Carried out as inExample 11 pared in Example 16 was stirred with a slurry of calciumexcept that the dispersion contained 35 g. of Philblack hydroxide (130parts) i water (40 parts) t reflux f 55 (trademark of Phillips Petroleumwith 6 1 hour. The water was removed by azeotropic distillation of thedefiocculating agent made-slug to 100 parts with t i ld d fi l ti agentL, xylene. The results are given in Ta e TABLE 2 EXAMPLE 18 I I Example13 was repeated except that 1n place of di- Deflocculating agent: Gradig methylaminoethyl methacrylate, 2-hydroxy propyl meth- Control 0acrylate (34.6 parts) was used. The resultant solution A g was used asdefiocculating agent M. g 7 EXAMPLE 19 D g Example 16 was repeatedexcept that in place of 4- E 3 vinyl pyridine, dimethylaminoethylmethacrylate (29.5 9 parts) was used, and in place of methacrylic acid,itaconic G acid (24.4 parts) was used, the latter being dissolved inEXAMPLE 13 the n-propanol before being added to the reaction vessel. 2Ethylhexyl acrylate (2652 parts), styrene (99.6 The resultant polymersolution was used as defiocculating agent N. parts) dimethylamlnoethylmethacrylate (37.7 parts), EXAMPLE 20 methacrylic acid (20.6 parts),toluene (440 parts), beu- 40 zene (440 parts) were placed in a stirredreaction vessel Th d fi l ti agents H, I, J d L, prepared i fitted witha stirrer and reflux condenser. This mixture Examples 13, 14, 15 and 17respectively, were tested as was brought to j below reflux temperatureand aZOdidispersants for carbon black as in Example 12. Thereisobutyronitrile (4.2 parts) stirred in toluene (40 parts) lt aregiven i Table 3, was added. The mixture was heated under reflux andportions of azodiisobutyronitrile (0.8 part) were added TABLE 3 every /2hour for 6 hours when polymerisation was substantially complete. Thissolution was used as deflocculat- Deflocculatmg agent' Gradmg ing agentH. I u 7 EXAMPLE 14 J 10 A portion 100 parts) of the polymer solutionprepared L 8 in Example 13 was stirred with a normal solution of sodiumhydroxide (17.1 ml.) heated under reflux for 1 EXAMPLE 21 hour. Thewater was removed by azeotropic distillation The defiocculating agentsH, K, M and N prepared in to yield defiocculating agent I. Examples 13,16, 18 and 19 respectively, were tested as EXAMPLE 15 dispersants forvarious pigments by grinding the pigment with defiocculating agent,morganic base and sufiiclent Example 14 was repeated except that aslurry of caltoluene to make up to 100 parts. Ingredients used andrecium hydroxide (1.26 parts) in water (40 parts) was used sultsobtained were as shown in Table 4.

TABLE 4 Solid defiocculating Inorganic base Pigment Parts Agent PartsParts Grading Philblack"55 35 H 3.5 Ca(OH) 0.15 10 Do 35 H 3.5Ba(OH)28H;O 0.53 10 35 K 3.5 0 0H: 0.15 10 35 M 3.5 Ca(OH) 0.16 7 35 N3.5 Ca(OH)n 0.14 10 30 H 1.2 0&(0H): 0.05 10 30 H 1.2 05 011), 0.05 10Supra Middle Chrome GA. H 1.2 Ca(OH)= 0.05 10 FastelViolet R,Supra 35 H3.5 Oa(OH) 0.15 10 FasteY' Pink R, Supra 35 H 3.5 Ca(OH)1 0.15 10Monastral Fast Blue BGA" 35 H 7.0 Ce(OH) 0.30 5

"Fastel" and "MonastraY are registered trademarks of Imperial ChemicalIndustries Ltd.

1 1 EXAMPLE 22 A typical gravure ink was made up using a 35% w./w.dispersion of Philblack 55 in a toluene which was made using the recipegiven in Table 4, first line. This dispersion was was ground until theaverage particle size was under one micron.

A portion of the ground dispersion (17.15 parts) was added slowly withhigh speed stirring to a mixture of a 60% w./w. zinc rosinate solutionin toluene (40 parts) and a 60% w./w. zinc rosinate solution in Boralene1127 (trademark) (40 parts). After thorough mixing toluene (2.85 parts)was added. This ink was then drawn down on paper and the latter wascompared with a dr-awdown of an ink made in the normal manner with nodeflocculating agent. Compared with the standard ink the dispersion inkwas at least 40% stronger in colour development.

EXAMPLE 23 A further portion of the dispersion prepared in Example 22was taken, precipitated into a large volume of acetone and separated byfiltration. The Philblack 55 pigment, coated with deflocculating agent,was then dried. A portion of this pigment (35 parts) was then groundwith toluene (65 parts). The resulting dispersion had a rating of 10.

We claim:

1. A dispersion comprising a pigment, a dispersion liquid selected fromaliphatic and aromatic hydrocarbons and mixtures thereof, and apolymeric deflocculating agent which is an addition copolymer comprisingfrom 99 to 50 mole percent of mer units derived from an ethylenicallyunsaturated monomer containing a solubilizing group Q such that thecompound QI-I is soluble in the dispersion liquid to the extent of atleast by weight and a total of from 1 to 50 mole percent of mer unitscarrying groups of internal salt structure, the said groups of internalsalt structure being formed from mer units selected from the groupconsisting of:

l I in combination with mer units selected from the group consisting of:

l I i wherein W is an alkyene group containing from 1 to 3 carbon atoms,R R and R are separately selected from hydrogen, alkyl, aralkyl and arylgroups containing from to seven carbon atoms, R; is selected fromhydrogen and alkyl groups containing from one to seven carbon atoms,

and R is R or -OR R being selected from alkyl and aryl groups containingfrom one to seven carbon atoms, and the polymeric deflocculating agentis present in an amount in the range of from 0.001 g. to 0.05 g.expressed as solid polymer for every 10 square metres of pigment surfacearea.

2. A dispersion according to claim 1 wherein the solubilising group Q isan alkyl group containing from 6 to 20 carbon atoms.

3. A dispersion according to claim 1 wherein the solubilising group isphenyl or benzyl.

4. A dispersion according to claim 1 comprising from 0.05 to 5% w./w.inclusive of water.

5. A dispersion according to claim 4 comprising from 0.5 to 2% w./w.inclusive of water.

6. A dispersion according to claim 1 wherein the polymericdeflocculating agent is a copolymer of Z-ethylhexylacrylate,dimethylaminoethyl methacrylate and acrylic acid.

7. A process of manufacturing the pigment dispersion of claim 1 whichcomprises grinding a mixture comprising a pigment, a dispersion liquidselected from aliphatic and aromatic hydrocarbons and mixtures thereofand, in an amount of from 0.001 g. to 0.05 g. expressed as solid polymerfor every 10 square meters of pigment surface area, a polymericdeflocculating agent which is an addition copolymer comprising from 99to 50 mole percent of mer units derived from an ethylenicallyunsaturated monomer containing a solubilizing group Q such that thecompound QH is soluble in the dispersion liquid to the extent of atleast 20% by weight and a total of from 1 to 50 mole percent of merunits carrying groups of internal salt structure, the said groups ofinternal salt structure being formed from mer units selected from thegroup consisting of:

in combination with mer units selected from the group consisting of:

Rr-COO' $134-$03- JIM- I- Ha l H: (13H: R5

wherein W is an alkylene group containing from 1 to 3 carbon atoms, R Rand R are separately selected from hydrogen, alkyl, aralkyl and arylgroups containing from one to seven carbon atoms, R is selected fromhydrogen and alkyl groups containing from one to seven atoms, and R orOR R being selected from alkyl and aryl groups containing from one toseven carbon atoms.

8. A process according to claim 7 wherein the mixture comprises, inaddition to the pigment, the dispersion liquid and the polymericdefiocculating agent, an inorganic base selected from the groupconsisting of alkaline earth metal hydroxides, alkali metal hydroxidesand ammonium hydroxide.

9. A process according to claim 8 wherein the mixture comprisessubstantially equimolar amounts of the inororganic base and thepolymeric deflocculating agent.

10. A process according to claim 7 wherein the poly- 1 mericdeflocculating agent is coated onto the pigment prior to grinding.

11. A process according to claim 8 wherein the polymeric defiocculatingagent is coated onto the pigment 1 prior to grinding.

References Cited UNITED STATES PATENTS Graves 26089.7 N Sloan 106308 NPrice 260-897 N Maeder et al. 260-897 N Melamed et a1. 26089.7 N Pellonet al. 260'80 PS Gardon et a1. 26033.6

DELBERT E. GANTZ, Primary Examiner S. L. BERGER, Assistant Examiner US.Cl. X.R.

